The effect of manganese additions on the structure changes proceeding in rapidly solidified Al‐Cu alloys

Abstract

The effect of Mn additions (0 ... 2 wt%) on the decomposition of rapidly solidified Al-1.0 wtyo Cu alloys (cooling rate lo3 to lo4 K/s; LQ treatment) were studied during ageing 1 letween RT and 450 "C by hardness, X-ray methods and electron microscopy. The results were compared with alloys homogenized in the region of the solid solution (SQ treatment).(i) The LQ treatment results in a quite better homogeneous distribution of the aIIoyed < lements than the SQ one, t h a t is less particles of intermetallic phases are present in the as-. i nst state. (ii) A t T < 250 "C Mn additions affect the decomposition kinetics by trapping trf vacancies (retardation) and the diminution of the solubility of Cu atoms (acceleration). The first effect dominates in the stage of G.P. zone formation, the second one during preci-1)itation of intermediate phases. (iii) At T 2 300 "C the intermetallic compound Cu,Mn,Al,, Jorms associated with a significant increase of the hardness. Der EinflulS von Mn-Zugaben (0 ... 2 wt%) auf die Entmischung schnell kristallisierter 41-4.0 wt% Cu-Legierungen (Abkiihlgeschwindigkeit von lo3 bis lo4 K/s; LQ-Behandlung) wurde mittels HBrtemessungen, Rontgenmethoden und Elektronenmikroskopie whhrend .ler Alterung zwischen RT und 450 "C untersucht. Die Ergebnisse wurden mit Legierungen verglichen, die aus dem Bereich der homogenen festen Losung abgeschreckt wurden (SQ-Behandlung).